U.S. patent application number 13/711769 was filed with the patent office on 2013-07-18 for organic electroluminescent device, lighting apparatus, and method for manufacturing the organic electroluminescent device.
The applicant listed for this patent is Shintaro Enomoto, Tomio Ono, Tomoaki SAWABE, Keiji Sugi. Invention is credited to Shintaro Enomoto, Tomio Ono, Tomoaki SAWABE, Keiji Sugi.
Application Number | 20130182418 13/711769 |
Document ID | / |
Family ID | 47563073 |
Filed Date | 2013-07-18 |
United States Patent
Application |
20130182418 |
Kind Code |
A1 |
SAWABE; Tomoaki ; et
al. |
July 18, 2013 |
ORGANIC ELECTROLUMINESCENT DEVICE, LIGHTING APPARATUS, AND METHOD
FOR MANUFACTURING THE ORGANIC ELECTROLUMINESCENT DEVICE
Abstract
According to one embodiment, an organic electroluminescent
device includes first and second electrodes, an interconnection
layer, an organic light emitting layer and a light scattering
layer. The first electrode has includes first, second and third
portions. The interconnection layer is electrically connected to
the first electrode. The third portion overlays the interconnection
layer when projected to the plane. The first and second portions do
not overlay the interconnection layer. The second electrode
overlays the second portion and does not overlay the first and the
third portions. The organic light emitting layer is provided
between the second portion and the second electrode. The second
portion is disposed between the fourth portion of the light
scattering layer and the second electrode. The fifth portion of the
light scattering layer overlays the interconnection layer. The
light scattering layer does not overlay the first portion when
projected to the plane.
Inventors: |
SAWABE; Tomoaki; (Tokyo,
JP) ; Ono; Tomio; (Kanagawa-ken, JP) ; Sugi;
Keiji; (Kanagawa-ken, JP) ; Enomoto; Shintaro;
(Kanagawa-ken, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAWABE; Tomoaki
Ono; Tomio
Sugi; Keiji
Enomoto; Shintaro |
Tokyo
Kanagawa-ken
Kanagawa-ken
Kanagawa-ken |
|
JP
JP
JP
JP |
|
|
Family ID: |
47563073 |
Appl. No.: |
13/711769 |
Filed: |
December 12, 2012 |
Current U.S.
Class: |
362/157 ; 257/40;
257/98; 438/29 |
Current CPC
Class: |
H01L 51/5212 20130101;
H01L 51/52 20130101; H01L 51/5268 20130101; F21L 4/00 20130101;
H01L 51/56 20130101; H01L 2251/5361 20130101; H01L 51/5225
20130101 |
Class at
Publication: |
362/157 ; 257/40;
257/98; 438/29 |
International
Class: |
H01L 51/52 20060101
H01L051/52; F21L 4/00 20060101 F21L004/00; H01L 51/56 20060101
H01L051/56 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 17, 2012 |
JP |
2012-007139 |
Claims
1. An organic electroluminescent device comprising: a first
electrode having a major surface and including a first portion, a
second portion arranged with the first portion in a first direction
parallel to the major surface and a third portion arranged with the
first portion in the first direction, the first electrode being
light transmissive; an interconnection layer extending in a plane
parallel to the major surface, the interconnection layer being
light-reflective and electrically connected to the first electrode,
and having a conductivity higher than a conductivity of the first
electrode, the third portion overlaying the interconnection layer
when projected to the plane, and the first portion and the second
portion not overlaying the interconnection layer when projected to
the plane; a second electrode being light-reflective, the second
electrode overlaying the second portion and not overlaying the
first portion and the third portion when projected to the plane; an
organic light emitting layer provided between the second portion
and the second electrode; and a light scattering layer including a
fourth portion and a fifth portion arranged with the fourth portion
in a direction parallel to the major surface, the second portion
being disposed between the fourth portion and the second electrode,
the fifth portion overlaying the interconnection layer when
projected to the plane, and the light scattering layer not
overlaying the first portion when projected to the plane.
2. The device according to claim 1, further comprising a substrate
provided between the first electrode and the light scattering
layer, the substrate being light transmissive.
3. The device according to claim 2, further comprising an
intermediate layer provided between the substrate and the first
electrode and including an irregular structure portion.
4. The device according to claim 1, wherein the second electrode
has a width not less than 1 micrometer and not more than 2000
micrometers.
5. The device according to claim 1, wherein the interconnection
layer has a strip-shaped portion extending along a direction
parallel to the plane, and a width of the interconnection layer is
not less than 1 micrometer and not more than 2000 micrometers, the
width being along the direction perpendicular to the extending
direction of the strip-shaped portion of the interconnection layer
and parallel to the plane.
6. The device according to claim 1, wherein the interconnection
layer includes at least one selected from the group consisting of
Mo, Ta, Nb, Al, Ni, and Ti.
7. The device according to claim 1, wherein a width of the first
electrode along a direction parallel to the plane is not less than
20 millimeters.
8. The device according to claim 1, wherein a light emitted from
the organic light emitting layer is a white light.
9. The device according to claim 1, wherein the second electrode
includes a plurality of strip-shaped first pattern portions
extending in a first direction parallel to the major surface.
10. The device according to claim 9, wherein the second electrode
further including a plurality of strip-shaped second pattern
portions extending along a second direction parallel to the major
surface and non-parallel to the first direction.
11. The device according to claim 1, wherein the second electrode
includes at least one of aluminum and silver.
12. The device according to claim 1, wherein the light scattering
layer includes a resin layer and a plurality of particles, the
particles being dispersed in the resin layer and having an average
diameter not less than 200 nanometers and not more than 100
micrometers.
13. The device according to claim 12, wherein an absolute value of
a difference between a refractive index of the resin layer and a
refractive index of the particles is not less than 0.1.
14. The device according to claim 1, wherein the light scattering
layer changes a travel direction of a light emitted from the
organic light emitting layer.
15. The device according to claim 1, wherein the light scattering
layer scatters a light reflected by the interconnection layer and
the second electrode.
16. The device according to claim 1, wherein the light scattering
layer scatters an external light incident upon at least one of the
interconnection layer and the second electrode.
17. The device according to claim 1, wherein the second electrode
has a grid pattern.
18. A lighting apparatus comprising: an organic electroluminescent
device including a first electrode having a major surface and
including a first portion, a second portion arranged with the first
portion in a first direction parallel to the major surface and a
third portion arranged with the first portion in the first
direction, the first electrode being light transmissive, an
interconnection layer extending in a plane parallel to the major
surface, the interconnection layer being light-reflective and
electrically connected to the first electrode, and having a
conductivity higher than a conductivity of the first electrode, the
third portion overlaying the interconnection layer when projected
to the plane, and the first portion and the second portion not
overlaying the interconnection layer when projected to the plane, a
second electrode being light-reflective, the second electrode
overlaying the second portion and not overlaying the first portion
and the third portion when projected to the plane, an organic light
emitting layer provided between the second portion and the second
electrode, and a light scattering layer including a fourth portion
and a fifth portion arranged with the fourth portion in a direction
parallel to the major surface, the second portion being disposed
between the fourth portion and the second electrode, the fifth
portion overlaying the interconnection layer when projected to the
plane, and the light scattering layer not overlaying the first
portion when projected to the plane; and a power supply unit
electrically connected to the interconnection layer and the second
electrode, and configured to supply a current passing through the
organic light emitting layer via the interconnection layer, the
first electrode, and the second electrode.
19. A method for manufacturing an organic electroluminescent device
comprising: preparing a workpiece including: a first electrode
having a major surface and including a first portion, a second
portion arranged with the first portion in a first direction
parallel to the major surface and third portion arranged with the
first portion in the first direction, the first electrode being
light transmissive; an interconnection layer extending in a plane
parallel to the major surface, the interconnection layer being
light-reflective and electrically connected to the first electrode,
and having a conductivity higher than a conductivity of the first
electrode, the third portion overlaying the interconnection layer
when projected to the plane and the first portion and the second
portion not overlaying the interconnection layer when projected to
the plane; a second electrode being light-reflective, the second
electrode overlaying the second portion and not overlaying the
first portion and the third portion when projected to the plane; an
organic light emitting layer provided between the second portion
and the second electrode; and a light scattering layer including a
fourth portion and a fifth portion arranged with the fourth portion
in a direction parallel to the major surface, the second portion
being disposed between the fourth portion and the second electrode,
the fifth portion overlaying the interconnection layer when
projected to the plane, and the light scattering layer not
overlaying the first portion when projected to the plane, the work
piece having a processing surface parallel to the plane; and
forming a light scattering layer on the processing surface by
exposure processing using the interconnection layer and the second
electrode as masks, the light scattering layer including a fourth
portion and a fifth portion arranged with the fourth portion in a
direction parallel to the major surface, the second portion being
disposed between the fourth portion and the second electrode, the
fifth portion overlaying the interconnection layer when projected
to the plane, and the light scattering layer not overlaying the
first portion when projected to the plane.
20. The method according to claim 19, wherein the forming the light
scattering layer includes forming a resin film on the processing
surface, the resin film capable to generate a photosensitivity, and
irradiating the resin film with a light to cause the
photosensitivity to be generated by using the interconnection layer
and the second electrode as masks to process the resin film into a
pattern reflecting pattern shapes of the interconnection layer and
the second electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2012-007139, filed on Jan. 17, 2012; the entire contents of which
are incorporated herein by reference.
FIELD
[0002] Embodiments described herein relate generally to an organic
electroluminescent device, a lighting apparatus, and a method for
manufacturing the electroluminescent device.
BACKGROUND
[0003] Recently, organic electroluminescent devices have been
attracting attentions for use as a flat light source. In the
organic electroluminescent device, an organic thin film is provided
between two electrodes. By applying a voltage to the organic thin
film to inject electrons and holes so that they may be recombined,
excitons are produced. When the excitons are radiatively
deactivated, light is emitted and utilized.
[0004] Due to their features such as thinness, lightweight, and
large area surface emission, the organic electroluminescent devices
are expected to find applications that have not been able to be
realized with the conventional lighting equipment and light
sources.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a schematic cross-sectional view illustrating an
organic electroluminescent device according to a first
embodiment;
[0006] FIG. 2 is a schematic plan view illustrating the organic
electroluminescent device according to the first embodiment;
[0007] FIG. 3 is a schematic plan view illustrating the organic
electroluminescent device according to the first embodiment;
[0008] FIG. 4A and FIG. 4B are schematic plan views illustrating
the organic electroluminescent device according to the first
embodiment;
[0009] FIG. 5 is a schematic cross-sectional view illustrating a
portion of the organic electroluminescent device according to the
first embodiment;
[0010] FIG. 6A to FIG. 6D are schematic cross-sectional views
illustrating portions of the organic electroluminescent device
according to the first embodiment;
[0011] FIG. 7A and FIG. 7B are schematic plan views illustrating
another organic electroluminescent device according to the first
embodiment;
[0012] FIG. 8A and FIG. 8B are schematic plan views illustrating
the organic electroluminescent device according to the first
embodiment;
[0013] FIG. 9A and FIG. 9B are schematic plan views illustrating
the organic electroluminescent device according to the first
embodiment;
[0014] FIG. 10 is a graph illustrating characteristics of the
organic electroluminescent device according to the first
embodiment;
[0015] FIG. 11A and FIG. 11B are schematic views illustrating a
usage state of the organic electroluminescent device according to
the first embodiment;
[0016] FIG. 12A and FIG. 12B are schematic views illustrating
another usage state of the organic electroluminescent device
according to the first embodiment;
[0017] FIG. 13 is a schematic cross-sectional view illustrating
another organic electroluminescent device according to the first
embodiment;
[0018] FIG. 14 is a schematic cross-sectional view illustrating
another organic electroluminescent device according to the first
embodiment;
[0019] FIG. 15A to FIG. 15C are schematic cross-sectional views
illustrating organic electroluminescent devices according to the
first embodiment;
[0020] FIG. 16A to FIG. 16C are schematic cross-sectional views
organic electroluminescent devices according to the first
embodiment;
[0021] FIG. 17 is a schematic view illustrating a lighting
apparatus according to a second embodiment;
[0022] FIG. 18A to FIG. 18E are schematic cross-sectional views
illustrating a method for manufacturing an organic
electroluminescent device according to a third embodiment in order
of processes;
[0023] FIG. 19A to FIG. 19D are schematic cross-sectional views
illustrating another method for manufacturing the organic
electroluminescent device according to the third embodiment in
order of processes; and
[0024] FIG. 20 is a flowchart illustrating the method for
manufacturing the organic electroluminescent device according to
the third embodiment.
DETAILED DESCRIPTION
[0025] According to one embodiment, an organic electroluminescent
device includes: a first electrode; an interconnection layer; a
second electrode; an organic light emitting layer; and a light
scattering layer. The first electrode has a major surface and
includes a first portion, a second portion arranged with the first
portion in a first direction parallel to the major surface and a
third portion arranged with the first portion in the first
direction. The first electrode is light transmissive. The
interconnection layer extends in a plane parallel to the major
surface. The interconnection layer is light-reflective and
electrically connected to the first electrode. The interconnection
layer has a conductivity higher than a conductivity of the first
electrode. The third portion overlays the interconnection layer
when projected to the plane. The first portion and the second
portion do not overlay the interconnection layer when projected to
the plane. The second electrode is light-reflective. The second
electrode overlays the second portion and does not overlay the
first portion and the third portion when projected to the plane.
The organic light emitting layer is provided between the second
portion and the second electrode. The light scattering layer
includes a fourth portion and a fifth portion arranged with the
fourth portion in a direction parallel to the major surface. The
second portion is disposed between the fourth portion and the
second electrode. The fifth portion overlays the interconnection
layer when projected to the plane. The light scattering layer does
not overlay the first portion when projected to the plane.
[0026] According to another embodiment, a lighting apparatus
includes an organic electroluminescent device and a power supply
unit. The organic electroluminescent device includes a first
electrode, an interconnection layer, a second electrode, an organic
light emitting layer, and a light scattering layer. The first
electrode has a major surface and includes a first portion, a
second portion arranged with the first portion in a first direction
parallel to the major surface and a third portion arranged with the
first portion in the first direction. The first electrode is light
transmissive. The interconnection layer extends in a plane parallel
to the major surface. The interconnection layer is light-reflective
and electrically connected to the first electrode. The
interconnection layer has a conductivity higher than a conductivity
of the first electrode. The third portion overlays the
interconnection layer when projected to the plane. The first
portion and the second portion do not overlay the interconnection
layer when projected to the plane. The second electrode is
light-reflective. The second electrode overlays the second portion
and does not overlay the first portion and the third portion when
projected to the plane. The organic light emitting layer is
provided between the second portion and the second electrode. The
light scattering layer includes a fourth portion and a fifth
portion arranged with the fourth portion in a direction parallel to
the major surface. The second portion is disposed between the
fourth portion and the second electrode. The fifth portion overlays
the interconnection layer when projected to the plane. The light
scattering layer does not overlay the first portion when projected
to the plane. The power supply unit is electrically connected to
the interconnection layer and the second electrode, and configured
to supply a current passing through the organic light emitting
layer via the interconnection layer, the first electrode, and the
second electrode.
[0027] According to another embodiment, a method is disclosed for
manufacturing an organic electroluminescent device. The method can
include preparing a workpiece. The workpiece includes: a first
electrode having a major surface and including a first portion, a
second portion arranged with the first portion in a first direction
parallel to the major surface and third portion arranged with the
first portion in the first direction, the first electrode being
light transmissive; an interconnection layer extending in a plane
parallel to the major surface, the interconnection layer being
light-reflective and electrically connected to the first electrode,
and having a conductivity higher than a conductivity of the first
electrode, the third portion overlaying the interconnection layer
when projected to the plane and the first portion and the second
portion not overlaying the interconnection layer when projected to
the plane; a second electrode being light-reflective, the second
electrode overlaying the second portion and not overlaying the
first portion and the third portion when projected to the plane; an
organic light emitting layer provided between the second portion
and the second electrode, the work piece having a processing
surface parallel to the plane. The method can include forming a
light scattering layer on the processing surface by exposure
processing using the interconnection layer and the second electrode
as masks. The light scattering layer includes a fourth portion and
a fifth portion arranged with the fourth portion in a direction
parallel to the major surface. The second portion is disposed
between the fourth portion and the second electrode. The fifth
portion overlays the interconnection layer when projected to the
plane. The light scattering layer does not overlay the first
portion when projected to the plane.
[0028] Various embodiments will be described hereinafter with
reference to the accompanying drawings.
[0029] The drawings are schematic or conceptual, so that the
relationship between thickness and width of each of the components
and the size ratio between the components are not always realistic.
Even the same component may be denoted with different sizes or
ratios in the different drawings.
[0030] In the specification and the drawings, identical reference
numerals are given to identical components in examples, and
detailed description on the identical components will be omitted
appropriately.
First Embodiment
[0031] FIG. 1 is a schematic cross-sectional view illustrating an
organic electroluminescent device according to first
embodiment.
[0032] FIG. 2 is a schematic plan view illustrating the organic
electroluminescent device according to the first embodiment. FIG. 1
is a cross-sectional view taken along line A1-A2 of FIG. 2.
[0033] Those figures illustrate the organic electroluminescent
device according to the embodiment by expanding a portion of this
device.
[0034] As shown in FIG. 1 and FIG. 2, an organic electroluminescent
device 110 according to the embodiment includes a first electrode
10, a second electrode 20, an interconnection layer 31, an organic
light emitting layer 40, and a light scattering layer 51.
[0035] The first electrode 10 has a first major surface 10a and a
second major surface 10b. The second major surface 10b is opposite
to the first major surface 10a. The first electrode 10 is light
transmissive. The first electrode 10 may be, for example, a
transparent electrode.
[0036] In this example, the organic electroluminescent device 110
further includes a light transmissive substrate 80. The substrate
80 is provided between the first electrode 10 and the light
scattering layer 51.
[0037] One direction parallel to the first major surface 10a is
taken to be an X-axis direction. A direction parallel to the first
major surface 10a and perpendicular to the X-axis is taken to be a
Y-axis direction. A direction perpendicular to the X-axis and the
Y-axis is taken to be a Z-axis direction. The Z-axis direction
corresponds to the thickness direction of the first electrode
10.
[0038] The interconnection layer 31 extends in a plane parallel to
the first major surface 10a. That is, the interconnection layer 31
extends in an X-Y plane. When projected to the X-Y plane, the first
electrode 10 has a portion that does not overlay the
interconnection layer 31.
[0039] For example, an interconnection portion 30 is provided,
which includes the conductive interconnection layer 31. The
interconnection layer 31 is provided except in an interconnection
layer non-formation region 32. When projected to the X-Y plane, the
interconnection layer non-formation region 32 overlays at least a
portion of the first electrode 10. For example, the interconnection
layer 31 overlays one portion of the first electrode 10 when
projected to the X-Y plane. The interconnection layer 31 is
electrically connected to the first electrode 10. For example, the
interconnection layer 31 is shaped like a strip or grid structure
extending in the X-Y plane.
[0040] As shown in FIG. 2, the interconnection layer 31 is
strip-shaped in this example. However, as described later, the
interconnection layer 31 may have an arbitrary pattern shape. The
interconnection layer 31 has a higher conductivity than the first
electrode 10. The interconnection layer 31 is light reflective. The
interconnection layer 31 may be, for example, a metal electrode.
The interconnection layer 31 functions as an auxiliary electrode
configured to send a current flowing through the first electrode
10. In this example the interconnection layer 31 is provided on the
first electrode 10. The interconnection layer 31 may be provided
under the first electrode 10. The interconnection layer 31 is
arranged to expose at least a portion of the first electrode
10.
[0041] The interconnection layer 31 has a higher optical
reflectivity than the first electrode 10. In the specification of
the application, the state of having a higher optical reflectivity
than the first electrode 10 is referred to as being light
reflective. An insulating layer (not shown) may be provided on the
upper surface and side surface of the interconnection layer 31.
[0042] The second electrode 20 faces the first major surface 10a of
the first electrode 10. The second electrode 20 is light
reflective. That is, the second electrode 20 has a higher optical
reflectivity than the first electrode 10.
[0043] The first electrode 10 has a higher optical transmittance
than the interconnection layer 31 and the second electrode 20. In
the specification, the state of having a higher optical
transmittance than the interconnection layer 31 and the second
electrode 20 is referred to as light transmissive. That is, the
substrate 80 has a higher optical transmittance than the
interconnection layer 31 and the second electrode 20.
[0044] The second electrode 20 has a conductive portion 21. The
conductive portion 21 is light reflective. When projected to the
X-Y plane, the conductive portion 21 overlays at least a portion of
a region that does not overlay the interconnection layer 31. That
is, the conductive portion 21 is provided except in a conductive
portion non-formation region 22. When projected to the X-Y plane,
the conductive portion non-formation region 22 is provided at least
in a portion of the region that does not overlay the
interconnection layer 31. In the second electrode 20, for example,
a plurality of conductive portion non-formation regions 22 are
provided. The conductive portion 21 is provided in a region other
than the conductive portion non-formation region 22.
[0045] As shown in FIG. 2, in this example, the conductive portion
21 of the second electrode 20 is shaped like a strip. However, as
described later, the conductive portion 21 of the second electrode
20 may have an arbitrary pattern shape.
[0046] The organic light emitting layer 40 is provided between the
first major surface 10a of the first electrode 10 and the second
electrode 20.
[0047] The first electrode 10 is provided between the light
scattering layer 51 and the second electrode 20. The light
scattering layer 51 has a portion that overlays the interconnection
layer 31 and the conductive portion 21 when it is projected to the
X-Y plane. That is, the light scattering layer 51 faces the light
reflective portion due to the interconnection layer 31 and the
second electrode 20. The light scattering layer 51 is provided
except in at least a portion of the region that does not overlay
the interconnection layer 31 or the conductive portion 21 when it
is projected to the X-Y plane. The light scattering layer 51 is not
provided in at least a portion of the region that overlays the
conductive portion non-formation region 22 when it is projected to
the X-Y plane. The light scattering layer 51 is not provided in at
least a portion of the region that overlays the interconnection
layer non-formation region 32 when it is projected to the X-Y
plane.
[0048] For example, a light scattering portion 50 is provided. The
light scattering portion 50 has the light scattering layer 51. A
non-scattering portion 52 is provided in a region where the light
scattering layer 51 is not provided. The light scattering
performance of the non-scattering portion 52 is lower than that of
the light scattering layer 51. The light scattering layer 51 has a
portion that overlays the interconnection layer 31 and the
conductive portion 21 when it is projected to the X-Y plane. When
projected to the X-Y plane, the non-scattering portion 52 overlays
at least a portion of the conductive portion non-formation region
22 and at least a portion of the interconnection layer
non-formation region 32.
[0049] That is, as shown in FIG. 1 and FIG. 2, the first electrode
10 includes a first portion 10p, a second portion 10q and a third
portion 10r. The second portion 10p is arranged with the first
portion 10p in a first direction parallel to the first major
surface 10a. The third portion 10r is arranged with the first
portion 10p in the first direction.
[0050] The interconnection layer 31 extends in a plane parallel to
the first major surface 10a. The interconnection layer 31 is
light-reflective and electrically connected to the first electrode
10. The interconnection layer 31 has a conductivity higher than a
conductivity of the first electrode 10. The third portion 10r
overlays the interconnection layer 31 when projected to the plane.
The first portion 10p and the second portion 10q do not overlay the
interconnection layer 31 when projected to the plane.
[0051] The second electrode 20 is light-reflective. The second
electrode 20 overlays the second portion 10q and does not overlay
the first portion 10p and the third portion 10r when projected to
the plane.
[0052] The organic light emitting layer 40 is provided between the
second portion 10q and the second electrode 20.
[0053] The light scattering layer 51 including a fourth portion 50p
and a fifth portion 50q. The fifth portion is arranged with the
fourth portion 50q in a direction parallel to the first major
surface 10a. The second portion 10q is disposed between the fourth
portion 50p and the second electrode 20. The fifth portion 50q
overlays the interconnection layer 31 when projected to the plane.
The light scattering layer 51 does not overlay the first portion
10p when projected to the plane.
[0054] In this example in which the substrate 80 is provided, the
light scattering layer 51 is partially provided on the major
surface of the substrate 80. The light scattering layer 51 has
substantially the same shape as the interconnection layer 31 and
the conductive portion 21. The embodiment is not limited to it; the
edge of the light scattering layer 51 may be either outside or
inside the edge of the interconnection layer 31 and the conductive
portion 21 when the layer 51 is projected to the X-Y plane. The
non-scattering portion 52 overlays at least a portion of the
conductive portion non-formation region 22 and at least a portion
of the interconnection layer non-formation region 32 when projected
to the X-Y plane, so that the organic electroluminescent device 110
becomes light transmissive.
[0055] As shown in FIG. 1, the organic light emitting layer 40 of
the portion where the first electrode 10 and the second electrode
20 (conductive portion 21) face each other provides a light
emitting region 44. Emitted light 45 produced by the light emitting
region 44 goes out of the organic electroluminescent device 110 via
the first electrode 10 and the light scattering layer 51. A portion
of the emitted light 45 is reflected by the second electrode 20 and
goes out via the first electrode 10 and the light scattering layer
51. A portion of those lights goes out via the non-scattering
portion 52. By providing the light scattering layer 51, the path of
the emitted light 45 is changed to reduce the light which may
return into the device through, for example, total reflection,
thereby enabling an efficient light extraction.
[0056] In the organic electroluminescent device 110, an external
light 46 entering from the outside passes through the conductive
portion non-formation region 22 of the second electrode 20, the
interconnection layer non-formation region 32, and the first
electrode 10. In such a manner, the organic electroluminescent
device 110 can transmit the outside light 46 incident upon the
organic electroluminescent device 110, while emitting the emitted
light 45.
[0057] Since the non-scattering portion 52 (for example, a portion
where the light scattering layer 51 is not provided) overlays the
conductive portion non-formation region 22 and the interconnection
layer non-formation region 32, the external light 46 is not
scattered substantially when it passes through the conductive
portion non-formation region 22, the interconnection layer
non-formation region 32, and the first electrode 10. As a result,
it is possible to form an image by using the external light 46
through the organic electroluminescent device 110. That is, the
organic electroluminescent device 110 is light transmissive.
[0058] By providing the light scattering layer 51 at a position
where the light reflective interconnection layer 31 and the
conductive portion 21 overlay each other when projected to the X-Y
plane, it is possible to scatter specular-reflection light at the
interconnection layer 31 and the conductive portion 21.
Accordingly, it is possible to suppress the reflected image of an
external image from being visually recognized.
[0059] In such a manner, the light scattering layer 51 changes the
direction in which the light emitted from the organic light
emitting layer 40 travels. The light scattering layer 51 can
scatter the light reflected by the interconnection layer 31 and the
conductive portion 21. The light scattering layer 51 can scatter
the external light 46 which is made incident upon at least one of
the interconnection layer 31 and the conductive portion 21. A
portion of the organic electroluminescent device 110 that overlays
the conductive portion non-formation region 22 and does not overlay
the light scattering layer 51 when it is projected to the X-Y plane
is transparent. Another portion of the organic electroluminescent
device 110 that overlays the interconnection layer non-formation
region 32 and does not overlay the light scattering layer 51 when
it is projected to the X-Y plane is transparent.
[0060] The organic electroluminescent device 110 according to the
embodiment is light transmissive (transparent) as described above.
Therefore, a background image can be visually recognized via the
organic electroluminescent device 110. In this case, if an external
image is specular-reflected by the interconnection layer 31 and the
conductive portion 21, for example, the image of an observer
himself is reflected by the interconnection layer 31 and the
conductive portion 21, so that a resultant reflected image is
visually recognized by the observer. That is, a reflected image of
the external image occurs. It significantly deteriorates the
visibility of the background image.
[0061] The organic electroluminescent device 110 according to the
embodiment can transmit light and, at the same time, suppress the
reflected image from being formed, thereby obtaining high
visibility of the background image.
[0062] In such a manner, according to the embodiment, it is
possible to provide a light transmissive and practical organic
electroluminescent device. According to the embodiment, a high
light emitting efficiency can be obtained. When the organic
electroluminescent device is applied to a lighting apparatus, its
lighting function and other functions to transmit a background
image enable a variety of new applications.
[0063] For example, an organic EL display device may possibly have
a configuration in which a plurality of pixels (light emitting
regions) are provided and a light transmissive region is provided
between the pixels. In this case, it is possible to suppress
reflection by the reflecting electrode by using, for example, a
circular polarization plate. However, the use of the circular
polarization plate decreases the transmittance as well as
transparency and also deteriorates the luminous efficiency. If the
light scattering layer is provided to reduce the formation of
reflection images in the light transmissive organic EL display
device, a problem occurs in that the effective resolution may
deteriorate in a plurality of pixels.
[0064] On the other hand, when an optical layer such as a circular
polarization plate is used to suppress the formation of reflection
images in a lighting apparatus which uses an organic
electroluminescent device, the transmittance and the luminous
efficiency decrease, thereby deteriorating usefulness. Further, in
contrast to the display device, which provides different light
emission for the different pixels, the use of the light scattering
layer 51 in a lighting apparatus does not give rise to the problem
in the deterioration of resolution. In the organic
electroluminescent device 110 according to the embodiment, by using
the light scattering layer 51, it is possible to obtain practical
lighting functions and background image transmittance functions
while suppressing the formation of reflection images.
[0065] Further, the organic EL display device has a small size of
the pixels and thus, has no manifest problem of a drop in potential
of the transparent electrode in the pixel.
[0066] On the other hand, if the organic electroluminescent device
is applied to a large-area lighting apparatus, the emission
luminance becomes non-uniform due to a potential drop caused by the
resistance of the first electrode 10. In this case, in the
embodiment, the low-resistance interconnection layer 31 is provided
to the first electrode 10 and the potential drop is suppressed. If
the interconnection layer 31 is made of a metal to provide the
low-resistance interconnection layer 31, specular reflection occurs
on the interconnection layer 31.
[0067] In the embodiment, the light scattering layer 51 has a
portion that overlays the interconnection layer 31 and the
conductive portion 21 when it is projected to the X-Y plane. It
will suppress the formation of a reflection image owing to the
second electrode 20 which faces the light emitting region 44 as
well as the formation of a reflection image owing to the
interconnection layer 31.
[0068] FIG. 3 is a schematic plan view illustrating the organic
electroluminescent device according to the first embodiment.
[0069] FIG. 1 and FIG. 2 already described illustrate the
configuration of a portion PA of the organic electroluminescent
device 110 illustrated in FIG. 3.
[0070] As shown in FIG. 3, the organic electroluminescent device
110 according to the embodiment has the first electrode 10, the
interconnection portion 30 connected to the first electrode 10, and
the second electrode 20 which faces the first electrode 10. In this
example, the organic light emitting layer 40 is omitted. As viewed
along the Z-axis, the organic electroluminescent device 110 appears
to be, for example, square (for example, rectangular). Each side of
the square is, for example, about not less than 20 mm and not more
than 2000 mm. For example, the width of the first electrode 10
parallel to the X-Y plane is not less than 20 mm and not more than
2000 mm. For example, the width of the first electrode 10 parallel
to the X-Y plane is not less than 50 mm.
[0071] FIG. 4A and FIG. 4B are schematic plan views illustrating
the organic electroluminescent device according to the first
embodiment.
[0072] FIG. 4A shows an example of the pattern shape of the second
electrode 20. FIG. 4B shows an example of the pattern shape of the
interconnection portion 30. The portion PA of the organic
electroluminescent device 110 shown in FIG. 4A and FIG. 4B
corresponds to a portion illustrated in FIG. 1 and FIG. 2.
[0073] As shown in FIG. 4A, in this example, the second electrode
20 (conductive portion 21) is shaped like a strip. In this example,
the second electrode 20 (conductive portion 21) extends along the
Y-axial direction. In the embodiment, the direction in which the
second electrode 20 (conductive portion 21) extends is
arbitrary.
[0074] As shown in FIG. 4B, in this example, the interconnection
portion 30 is shaped like a strip. In this example, the
interconnection portion 30 extends along the Y-axial direction. In
the embodiment, the direction in which the interconnection portion
30 extends is arbitrary.
[0075] In the embodiment, if the second electrode 20 (conductive
portion 21) is strip-shaped and the interconnection portion 30 is
strip-shaped, the relationship between the direction in which the
strip of the second electrode 20 (conductive portion 21) extends
and the direction in which the strip of the interconnection portion
30 extends is arbitrary. The direction in which the strip of the
second electrode 20 (conductive portion 21) extends is parallel or
non-parallel (sloped or perpendicular) to the direction in which
the strip of the interconnection portion 30 extends. Examples of
the pattern of the second electrode 20 (conductive portion 21) and
the pattern of the interconnection portion 30 will be described
later.
[0076] The following will describe examples of the layers included
in the organic electroluminescent device 110.
[0077] FIG. 5 is a schematic cross-sectional view illustrating a
portion of the organic electroluminescent device according to the
first embodiment.
[0078] As shown in FIG. 5, the organic light emitting layer 40
includes a light emitting portion 43. The organic light emitting
layer 40 can further include at least one of a first layer 41 and a
second layer 42 as necessary. The light emitting portion 43 emits a
light including the wavelength of a visible light. The first layer
41 is provided between the light emitting portion 43 and the first
electrode 10. The second layer 42 is provided between the light
emitting portion 43 and the second electrode 20.
[0079] As the material of the light emitting portion 43, for
example, Alq.sub.3 (tris(8-hydroxyquinolinolato) aluminum),
F8BT(poly 9,9-dioctylfluorene-co-benzothiadiazole), and
PPV(polyparaphenylene vinylene) can be used. The light emitting
portion 43 can be made of a mixed material including a host
material and a dopant to be added to the host material. As the host
material, for example, CBP (4,4'-N,N'-bis-dicarbazolylbiphenyl),
BCP (2.9-dimethyl-4,7-diphenyl-1,10-phenanthroline), TPD
(4,4'-bis[N-(3-methyl phenyl)-N-phenylamino]biphenyl), PVK
(polyvinyl carbazole), and PPT (poly(3-phenylthiophene)) can be
used. As the dopant material, for example, FIrpic
(iridium(III)bis(4,6-difluorophenyl)pyridinato-N,C2'-picolinate,
Ir(ppy).sub.3(Tris(2-phenylpyridine)iridium), and
FIr6(bis(2,4-difluorophenyl pyridinato)-tetrakis(1-pyrazolil)
borate Iridium (III) can be used.
[0080] The first layer 41 functions as, for example, a hole
injection layer. The first layer 41 functions as, for example, a
hole transport layer. The first layer 41 may have, for example, a
stacked structure including a layer which functions as the hole
injection layer and a layer which functions as the hole transport
layer. The first layer 41 may include another layer other than the
layer which functions as the hole injection layer and the layer
which functions as the hole transport layer.
[0081] The second layer 42 functions as, for example, an electron
injection layer. The second layer 42 can include, for example, a
layer which functions as an electron transport layer. The second
layer 42 may have, for example, a stacked structure including a
layer which functions as the electron injection layer and a layer
which functions as the electron transport layer. The second layer
42 may include another layer other than the layer which functions
as the electron injection layer and the layer which functions as
the electron transport layer.
[0082] For example, the organic light emitting layer 40 emits light
including visible light wavelengths. For example, the light emitted
from the organic light emitting layer 40 is substantially white
light. That is, the light emitted from the organic
electroluminescent device 110 is white light. "White light" as
referred to here is substantially white in color and includes, for
example, red-based, yellow-based, green-based, blue-based, and
purple-based white light.
[0083] The first electrode 10 includes an oxide including at least
one element selected from a group including, for example, In, Sn,
An, and Ti. The first electrode 10 can be formed of, for example,
an indium tin oxide (ITO) film. The first electrode 10 functions
as, for example, an anode.
[0084] The second electrode 20 includes at least one of, for
example, aluminum and silver. For example, the second electrode 20
is formed of an aluminum film. Further, the second electrode 20 may
be made of an alloy of silver and magnesium. Calcium may be added
to this alloy. The second electrode 20 functions as, for example, a
cathode.
[0085] The interconnection portion 30 includes at least one of a
group including, for example, Mo, Ta, Nb, Ni, and Ti. The
interconnection portion 30 may be, for example, a mixed film
including an element selected from this group. The interconnection
portion 30 may be a stacked film including those elements. The
interconnection portion 30 may be a stacked film of, for example,
Nb/Mo/Al/Mo/Nb. The interconnection portion 30 functions as an
auxiliary electrode that suppresses a potential drop at, for
example, the first electrode 10. The interconnection portion 30 can
function as a lead electrode configured to supply a current.
[0086] The substrate 80 may be made of, for example, a glass
substrate or a resin substrate.
[0087] FIG. 6A to FIG. 6D are schematic cross-sectional views
illustrating a portion of the organic electroluminescent device
according to the first embodiment.
[0088] Those figures illustrate the configuration of the light
scattering portion 50.
[0089] As shown in FIG. 6A, the light scattering portion 50
includes a resin layer 55 and a plurality of particles 56 dispersed
in the resin layer 55. The resin layer 55 is made of, for example,
a polysiloxane-based polymer. However, the material of the resin
layer 55 is arbitrary. The particle 56 may be at least one of, for
example, a silica particle and a polyethylene particle. However,
the material of the particle 56 is arbitrary. The diameter of the
particle 56 is, for example, not less than 0.2 .mu.m and not more
than 100 .mu.m. The thickness of the resin layer 55 is, for
example, not less than 0.2 .mu.m and not more than 100 .mu.m.
[0090] The absolute value of a difference between the refractive
index of the resin layer 55 and that of the particle 56 should
preferably be, for example, not less than 0.1 and, more preferably,
not less than 0.2. If the absolute value of the difference between
the refractive index of the resin layer 55 and that of the particle
56 is small, scattering characteristics is lower. By setting the
absolute value of the difference in refractive index not less than
0.1, sufficient scattering performance can be obtained. The
particle 56 may be shaped like a ball (including a flattened ball),
a polyhedral cube, and a needle.
[0091] For example, the refractive index of the resin layer 55 is
equivalent to that of the substrate 80. The absolute value of the
difference between the refractive index of the resin layer 55 and
that of the substrate 80 is less than 0.2. The resin layer 55 is
transparent.
[0092] As shown in FIG. 6B, in the light scattering portion 50, the
plurality of particles 56 may be disposed to come in contact with
each other.
[0093] As shown in FIG. 6C, in the light scattering portion 50, a
portion of the surface of the particle 56 may be exposed.
[0094] As shown in FIG. 6D, as the light scattering portion 50, a
transparent layer 57 having irregularities formed on its surface
can be used. For example, as the light scattering portion 50, the
transparent layer 57 having arbitrary irregularities are formed in
its surface can be used, such as a microlens layer, a groove layer,
or a pyramid layer. The transparent layer 57 may be made of a
polysiloxane-based polymer. The transparent layer 57 may contain a
component other than a resin such as filler.
[0095] The light scattering portion 50 is formed on, for example
the back surface of the substrate 80 (opposite side surface of the
substrate 80 with respect to the first electrode 10). The light
scattering portion 50 can be formed by a method such as coating or
printing by use of, for example, a raw material such as a solution
of the resin layer 55 containing the particle 56. For example, the
method may include spin coating, gravure printing, meniscus
coating, capillary coating, and slit coating.
[0096] As described later, the light scattering portion 50 may be
formed by a self-alignment method by use of the second electrode 20
and the interconnection portion 30.
[0097] As the light scattering portion 50, a sheet can be used in
which microlens-shaped or pyramid-shaped irregularities are
partially formed. A portion where the irregularities are formed
provides the light scattering layer 51 and a portion where the
irregularities are not formed provides the non-scattering portion
52. In the case of using such a sheet, an alignment mechanism is
used to align, for example, the substrate 80 and this sheet so that
they may be stuck to each other.
[0098] The light scattering portion 50 may employ a configuration
in which, for example, the resin layer 55 in which the particles 56
are dispersed is stacked with the sheet having microlens-shaped or
pyramid-shaped irregularities partially formed.
[0099] FIG. 7A and FIG. 7B are schematic plan views illustrating
another organic electroluminescent device according to the first
embodiment.
[0100] FIG. 7A shows an example of a pattern shape of the second
electrode 20 of an organic electroluminescent device 111 according
to the embodiment. FIG. 7B shows an example of the pattern shape of
the interconnection layer 31 of the organic electroluminescent
device 111. For example, cross-sectional views (taken along line
A1-A2) of a portion of the organic electroluminescent device 111
shown in FIG. 7A and FIG. 7B are the same as FIG. 1.
[0101] As shown in FIG. 7A, in the organic electroluminescent
device 111, the second electrode 20 (conductive portion 21) has a
grid configuration. In this example, the shape of the conductive
portion non-formation region 22 provided on the second electrode 20
is square (rectangular), however is not limited to square but
arbitrary.
[0102] Further, as shown in FIG. 7B, the interconnection layer 31
has a grid configuration. In this example, the shape of the
interconnection layer non-formation region 32 provided on the
interconnection portion 30 is square (rectangular), however is not
limited to square but arbitrary.
[0103] FIG. 8A and FIG. 8B are schematic plan views illustrating
the organic electroluminescent device of the first embodiment.
[0104] FIG. 8A shows the configuration in a case where the second
electrode 20 is strip-shaped and FIG. 8B shows the configuration in
a case where the second electrode 20 is grid-shaped. As shown in
FIG. 8A, the second electrode 20 (conductive portion 21) extends,
for example, along the Y-axis direction. In such a manner, the
second electrode 20 can include a plurality of strip-shaped
portions (first pattern portions 20p) which extend in a first
direction (Y-axis direction in this case) parallel to the first
major surface 10a. An X-axis directional length of the second
electrode 20 is taken to be a width wx2. An X-axis directional
center-to-center distance of the two neighboring second electrodes
20 (conductive portions 21) among the plurality of second
electrodes 20 (conductive portions 21) is taken to be a pitch
px2.
[0105] As shown in FIG. 8B, the second electrode 20 (conductive
portion 21) further has a portion (strip-shaped portion) which
extends along the X-axis direction. In such a manner, the second
electrode 20 can further include a plurality of second pattern
portions 20q which extend along a second direction (X-axis
direction in this example) parallel to the first major surface 10a
and non-parallel to the first direction. The Y-axis directional
length of the portion (strip-shaped portion, the second pattern
portion 20q) of the second electrode 20 that extends along the
X-axis direction is taken to be a width wy2. A Y-axis directional
center-to-center distance of the above two portions neighboring in
the Y-axis direction of the above portion (second pattern portion
20q) of the plurality of second electrodes 20 (conductive portions
21) is taken to be a pitch py2.
[0106] For example, at least one of the width wx2 and the width wy2
is not less than 1 .mu.m and not more than 2000 .mu.m.
Specifically, at least one of the width wx2 and the width wy2 is
not less than 10 .mu.m. By setting the widths wx2 and wx2 not less
than 10 .mu.m, manufacture becomes easy. The widths wx2 and wy2 are
not more than 500 .mu.m. By setting the widths wx2 and wy2 not more
than 500 .mu.m, the second electrode 20 becomes less conspicuous.
At least one of the widths wx2 and wy2 is, for example, not less
than 10 .mu.m and not more than 200 .mu.m.
[0107] At least one of the pitches px2 and py2 is not less than 50
.mu.m and not more than 5000 .mu.m.
[0108] For example, the pitches px2 and py2 are set to not less
than 400 .mu.m and not more than 500 .mu.m and the widths wx2 and
wy2 are set not less than 40 .mu.m and not more than 60 .mu.m. In
this case, the second electrode 20 can be formed by
photolithography and etching.
[0109] For example, the pitches px2 and py2 are set to not less
than 800 .mu.m and not more than 1000 .mu.m and the widths wx2 and
wy2 are set not less than 80 .mu.m and not more than 120 .mu.m. In
this case, the second electrode 20 can be formed by, for example,
deposition (for example, vacuum evaporation, sputtering etc.) and
patterned by use of a metal mask.
[0110] FIG. 9A and FIG. 9B are schematic plan views illustrating
the organic electroluminescent device of the first embodiment.
[0111] FIG. 9A shows the configuration in a case where the
interconnection layer 31 is strip-shaped and FIG. 9B shows the
configuration in a case where the interconnection layer 31 is
grid-shaped. As shown in FIG. 9A, the interconnection layer 31
extends, for example, along the Y-axis direction. That is, the
interconnection layer 31 has a strip-shaped portion that extends,
for example, along the Y-axis direction. The X-axis directional
length of the interconnection layer 31 is taken to be a width wx3.
An X-axis directional center-to-center distance of the two
neighboring interconnection layers 31 among the plurality of
interconnection layers 31 is taken to be a pitch px3.
[0112] As shown in FIG. 9B, the interconnection layer 31 further
has a portion that extends along the X-axis direction. A Y-axis
directional length of the portion (strip-shaped portion) of the
interconnection layer 31 that extends along the X-axis direction is
taken to be a width wy3. A Y-axis directional center-to-center
distance of the above two neighboring portions among the above
portions of the plurality of interconnection layers 31 is taken to
be a pitch py3.
[0113] For example, at least one of the width wx3 and the width wy3
is not less than 1 .mu.m and not more than 2000 .mu.m.
Specifically, at least one of the widths wx3 and wy3 is not less
than 10 .mu.m. By setting the widths wx3 and wy3 not less than 10
.mu.m, manufacture becomes easy. Further, highly conductive
interconnection layers 31 enhance in-plane uniformity of the
emission intensity. On the other hand, the widths wx3 and wy3 are
not more than 500 .mu.m. By setting the widths wx2 and wy2 not more
than 500 .mu.m, the interconnection layer 31 becomes less
conspicuous. At least one of the widths wx3 and wy3 is set, for
example, not less than 10 .mu.m and not more than 200 .mu.m.
[0114] At least one of the pitches px3 and py3 is set, for example,
not less than 50 .mu.m and not more than 5000 .mu.m.
[0115] For example, the pitches px3 and py3 are set not less than
400 .mu.m and not more than 500 .mu.m and the widths wx3 and wy3
are set not less than 40 .mu.m and not more than 60 .mu.m. In this
case, the interconnection layer 31 can be formed by, for example,
photolithography and etching.
[0116] For example, the pitches px3 and py3 are set not less than
800 .mu.m and not more than 1000 .mu.m and the widths wx3 and wy3
are set not less than 80 .mu.m and not more than 120 .mu.m. In this
case, the interconnection layer 31 can be formed by, for example,
deposition (for example, vacuum evaporation, sputtering etc.) and
patterned by use of a metal mask.
[0117] In the embodiment, if the pattern line widths of the second
electrode 20 and the interconnection portion 30 are large (the
conductive portion 21 and the interconnection layer 31 are wide),
the second electrode 20 and the interconnection portion 30 can be
observed easily and is conspicuous. If the second electrode 20 and
the interconnection portion 30 are conspicuous, it is difficult to
recognize a background image.
[0118] The inventors of the application have discussed conditions
for making the second electrode 20 and the interconnection portion
30 less conspicuous. In a specimen used in the discussion, a
plurality of strip-shaped Ag films are provided on a glass
substrate. The Ag films correspond to the second electrode 20 and
the interconnection portion 30. The Ag film has a strip-shaped
pattern pitch (which corresponds to the pitches py2 and py3) set to
a constant value of 200 .mu.m. The specimen used has a width of an
Ag-film strip-shaped pattern (which corresponds to the widths wy2
and wy3) set to a variable value between 20 .mu.m and 100 .mu.m. It
is noted that, when the width of the Ag-film strip-shaped pattern
is 100 .mu.m, an aperture ratio is 50%. By disposing white paper
behind the specimen and setting a distance between the specimen and
an observer to 0.3 m, an observable minimum width of the Ag-film
strip-shaped pattern was obtained. The observer had eyesight of 1.2
and was inside the room under fluorescent light as an evaluation
environment.
[0119] As a result, if the plurality of Ag-film strip-shaped
patterns are not less than 50 .mu.m, they could be observed to be
separate from each other, whereas if they are not more than 40
.mu.m (aperture ratio: 71%), they could not be observed. That is,
if they are not more than 40 .mu.m, the entirety of the specimen
was observed as a gray region with a decreased transmittance.
Further, if the width was 20 .mu.m (aperture ratio: 83%), a
difference between brightness of the region where the strip-shaped
patterns were provided and that of the other region decreased,
resulting in smaller sense of discomfort.
[0120] In such a manner, in the embodiment, the aperture ratio of
the second electrode 20 (for example, ratio of a total of areas of
the X-Y plane to which the plurality of conductive portion
non-formation regions 22 with respect to the area of the X-Y plane
to which the conductive portion 21 is projected) is, for example,
not less than 71%. Further, the aperture ratio of the second
electrode 20 is, for example, not less than 83%. By enhancing the
aperture ratio of the second electrode 20, the transmittance of the
organic electroluminescent device is improved. However, if the
aperture ratio increases, the area of the light emitting region 44
decreases.
[0121] Similarly, in the embodiment, the aperture ratio of the
interconnection portion 30 is, for example, not less than 71%. The
aperture ratio of the interconnection portion 30 is, for example,
not less than 83%.
[0122] In a display device, it is said that if the angle of sight
of the width of one pixel as viewed from the observer is about not
more than 0.028 degree, the pixel becomes invisible
(indistinguishable). This substantially agrees with the above
results that if the width is not more than 40 .mu.m when a distance
D between the specimen and the observer is 30 cm, the strip-shaped
patterns cannot be seen.
[0123] FIG. 10 is a graph illustrating characteristics of the
organic electroluminescent device according to the first
embodiment.
[0124] FIG. 10 illustrates a relationship between the distance D
between the organic electroluminescent device and the observer and
a pattern width wa at which the patterns cannot be observed. Its
horizontal axis gives the distance D and its vertical axis gives
the pattern width wa. The pattern width wa corresponds to the
maximum widths wx2, wy2, wx3, and wxy3.
[0125] As shown in FIG. 10, the pattern width wa at which the
patterns cannot be observed is proportional to the distance D. When
the distance D is 0.3 m, the pattern width wa is 40 .mu.m. When the
distance D is 6 m, the pattern width wa is 800 .mu.m.
[0126] In a case where the organic electroluminescent device
according to the embodiment is used in lighting, the distance D
between the relevant lighting apparatus and the user (observer) can
be changed variously. In the embodiment, based on the distance D in
accordance with usage, the widths wx2, wy2, wx3, and wy3 are
determined.
[0127] The following will describe an example of usage of the
organic electroluminescent device according to the embodiment.
Although in the following, a case is assumed where the organic
electroluminescent device 110 is used, the organic
electroluminescent device 111 may be used.
[0128] FIG. 11A and FIG. 11B are schematic views illustrating a
usage state of the organic electroluminescent device according to
the first embodiment.
[0129] FIG. 11A corresponds to a state (lighting state) where the
emitted light 45 is radiated from the organic lighting layer 40 and
FIG. 11B corresponds to a state (not lighting state) where the
emitted light 45 is not being radiated from it. As shown in these
figures, in this example, the second electrode 20 faces an observer
71 and the light scattering layer 51 faces an object 72.
[0130] As shown in FIG. 11A, in the lighting state, the object 72
is illuminated with the emitted light 45. Further, a portion of the
external light 46 is reflected by the second electrode 20 and
reaches the observer 71. Another portion of the external light 46
passes through the organic electroluminescent device 110, reaches
the object 72, is reflected by the object 72, and reaches the
observer 71 via the organic electroluminescent device 110. For
example, it is taken that the reflection coefficient and the
transmittance of the organic electroluminescent device 110 to be Ro
and To, respectively and the reflection coefficient of the object
72 to be Rb. The intensity of the emitted light 45 is taken to be
To and that of the external light 46, to be Is. In this case, the
intensity I of light that reaches the observer 71 is
(Io+Is)RbTo+IsRo.
[0131] As shown in FIG. 11B, in the not lighting state, the
intensity I of light that reaches the observer 71 is
IsRbTo+IsRo.
[0132] FIG. 12A and FIG. 12B are schematic views illustrating
another usage state of the organic electroluminescent device
according to the first embodiment.
[0133] FIG. 12A corresponds to the lighting state and FIG. 12B
corresponds to the not lighting state. As shown in those figures,
in this example, the light scattering layer 51 faces to the
observer 71 and the second electrode 20 faces to the object 72.
[0134] As shown in FIG. 12A, in the lighting state, the emitted
light 45 goes out toward the observer 71. Then, a portion of the
external light 46 is reflected by the second electrode 20 and
reaches the observer 71. Another portion of the external light 46
passes through the organic electroluminescent device 110, reaches
the object 72, is reflected by the object 72, and reaches the
observer 71 via the organic electroluminescent device 110. For
example, the reflection coefficient and the transmittance of the
organic electroluminescent device 110 are taken to be Ro' and To',
respectively. The intensity of the light that reaches the observer
71 is IsRbTo+To+IsRo'.
[0135] As shown in FIG. 12B, in the lighting state, the intensity I
of the light that reaches the observer 71 is IsRbTo+IsRo'.
[0136] In this usage state, in the not lighting state, the observer
71 can observe the object 72 via the organic electroluminescent
device 110. In the lighting state, owing to the emitted light 45
emitted from the organic electroluminescent device 110, the
observer 71 finds it difficult to see the object 72.
[0137] FIG. 13 is a schematic cross-sectional view illustrating
another organic electroluminescent device according to the first
embodiment.
[0138] FIG. 13 is a cross-sectional view corresponding to the cross
sections taken along line A1-A2 of FIG. 2, 4A, and FIG. 4B.
[0139] As shown in FIG. 13, in the another organic
electroluminescent device 112 according to the embodiment, the
second electrode 20 is provided on the substrate 80 and the organic
light emitting layer 40 is provided on the second electrode 20. The
first electrode 10 is provided on the organic light emitting layer
40 and the interconnection portion 30 is provided on the first
electrode 10. The light scattering portion 50 is provided on the
interconnection portion 30 and the upper surface of the first
electrode 10. The organic electroluminescent device 112 also can
provide a light transmissive organic electroluminescent device. It
is also possible to provide the interconnection portion 30 on the
organic light emitting layer 40 and the first electrode 10 on the
interconnection portion 30.
[0140] FIG. 14 is a schematic cross-sectional view illustrating
another organic electroluminescent device according to the first
embodiment.
[0141] As shown in FIG. 14, in another organic electroluminescent
device 112a according to the first embodiment, irregularities are
formed in a portion of the opposite side surface of the substrate
80 with respect to the first electrode 10. The irregularities
provide the light scattering layer 51 and the portion where the
irregularities are not formed provides the non-scattering portion
52. In such a manner, at least a portion of the substrate 80 may be
used as the light scattering portion 50.
[0142] FIG. 15A to FIG. 15C are schematic cross-sectional views
illustrating organic electroluminescent devices according to the
first embodiment.
[0143] Those figures are cross-sectional views corresponding to the
cross sections taken along line A1-A2 of FIG. 2, 4A, and FIG.
4B.
[0144] As shown in FIG. 15A, in another organic electroluminescent
device 113 according to the embodiment, the light scattering
portion 50 is provided between the substrate 80 and the first
electrode 10. At a portion between the substrate 80 and the first
electrode 10 where the light scattering layer 51 is not provided (A
non-scattering portion 52), a transmission layer 60 which transmits
the emitted light 45 is provided. The transmission layer 60 is made
of, for example, transparent resin etc. The transmission layer 60
is provided as necessary and may be omitted. For example, on the
substrate 80, the light scattering layer 51 and the transmission
layer 60 are provided. The first electrode 10 is provided thereon,
the interconnection portion 30 is provided on the first electrode
10, and the organic light emitting layer 40 is provided on the
first electrode 10. The second electrode 20 is provided on the
organic light emitting layer 40.
[0145] In the organic electroluminescent device 113, a distance
between the reflective electrodes (second electrode 20) that forms
an image due to reflection and the light scattering layer
decreases. Accordingly, even if the angle for visual recognition
changes, it is difficult to form an image by reflection.
[0146] As shown in FIG. 15B, in another organic electroluminescent
device 113a according to the embodiment, the light scattering
portion 50 is provided between the substrate 80 and the first
electrode 10. The transmission layer 60 is provided so that the
light scattering layer 51 may be embedded. That is, the
transmission layer 60 is provided to the non scattering portion 52
(between the light scattering layers 51) and between the light
scattering layer 51 and the first electrode 10.
[0147] As shown in FIG. 15C, in a further organic
electroluminescent device 113b according to the embodiment, on the
surface of the substrate 80 that faces the first electrode 10, the
light scattering portion 50 is provided. That is, irregularities
are formed in the surface of the substrate 80 to provide the light
scattering layer 51. That is, at least a portion of the substrate
80 is used as the light scattering layer 51. The transmission layer
60 is provided between the substrate 80 and the first electrode 10.
The transmission layer 60 flattens the irregularities. It is thus
possible to, for example, form the first electrode 10 stably.
[0148] In such a manner, in the embodiment, the layers and the
order in which the electrodes and the substrate are stacked can be
changed variously.
[0149] FIG. 16A to FIG. 16C are schematic cross-sectional views
illustrating organic electroluminescent devices according to the
first embodiment.
[0150] Those figures are cross-sectional views corresponding to
cross sections taken along line A1-A2 of, for example, FIG. 2, FIG.
4A, and FIG. 4B.
[0151] As shown in FIG. 16A, another organic electroluminescent
device 114 according to the embodiment, in the configuration of the
organic electroluminescent device 110 described with reference to
FIG. 1A to FIG. 1C, includes an intermediate layer 63 provided
between the substrate 80 and the first electrode 10 (that is,
between the light scattering portion 50 and the first electrode
10).
[0152] The intermediate layer 63 includes a high refractive-index
portion 61 and an irregular-structure portion 62. The high
refractive-index portion 61 is in contact with the first electrode
10. The refractive index of the high refractive-index portion 61 is
almost the same as that of the first electrode 10. The absolute
value of a difference between the refractive index of the high
refractive-index portion 61 and that of the first electrode 10 is,
for example, not more than 0.2. The refractive index of the high
refractive-index portion 61 is not less than 1.8 and not more than
2.0. The refractive index of the high refractive-index portion 61
is almost the same as that of the organic light emitting layer 40.
The high refractive-index portion 61 has a function to flatten the
surface of the irregular-structure portion 62.
[0153] The irregular-structure portion 62 is in contact with the
substrate 80. The irregular-structure portion 62 has a portion that
overlays the interconnection layer 31 and the conductive portion 21
when it is projected to the X-Y plane. The irregular-structure
portion 62 is provided except at least a portion of a region that
does not overlay the interconnection layer 31 or the conductive
portion 21 when it is projected to the X-Y plane. The
irregular-structure portion 62 has substantially the same pattern
shape as that of, for example, the light scattering layer 51.
[0154] As the irregular-structure portion 62, at least one of a
resin layer in which particles are scattered and a layer partially
having microlens-shaped or pyramid-shaped irregularities formed on
it can be used.
[0155] In the organic electroluminescent device 114, light that
propagates at least one of the inside of the organic light emitting
layer 40 and the inside of the first electrode 10 can be taken out.
It is thus possible to obtain a higher luminous efficiency.
[0156] As shown in FIG. 16B, in another organic electroluminescent
device 114a of the embodiment, the intermediate layer 63 is
provided between the substrate 80 and the first electrode 10, so
that irregularities 64 are formed in a portion of a surface of the
substrate 80 that corresponds to the intermediate layer 63. The
irregularities 64 correspond to the irregular-structure portion 62.
In this case also, light that propagates at least one of the inside
of the organic light emitting layer 40 and the inside of the first
electrode 10 can be taken out.
[0157] As shown in FIG. 16C, in another organic electroluminescent
device 114b according to the embodiment, the irregularities 64 are
formed and, further, irregularities are formed in a portion of the
opposite side surface of the substrate with respect to the first
electrode 10 so that those irregularities may provide the light
scattering layer 51 and the portion where the irregularities are
not formed may provide the non-scattering portion 52.
Second Embodiment
[0158] FIG. 17 is a schematic view illustrating a lighting
apparatus according to a second embodiment.
[0159] As shown in FIG. 17, a lighting apparatus 210 according to
the embodiment includes an organic electroluminescent device (for
example, the organic electroluminescent device 110) according to
the first embodiment and a power supply unit 201.
[0160] The power supply unit 201 is electrically connected to an
interconnection portion 30 and a second electrode 20. The power
supply unit 201 supplies a current passing through an organic light
emitting layer 40 via an interconnection portion 30, a first
electrode 10, and the second electrode 20.
[0161] The lighting apparatus 210 according to the embodiment can
provide a light transmissive lighting apparatus.
Third Embodiment
[0162] The embodiment relates to a method for manufacturing an
organic electroluminescent device. The embodiment corresponds
partially to a method for manufacturing a lighting apparatus.
[0163] FIG. 18A to FIG. 18E are schematic cross-sectional views
illustrating a method for manufacturing an organic
electroluminescent device according to a third embodiment in order
of processes.
[0164] As shown in FIG. 18A, a first electrode 10 is formed on, for
example, a substrate 80. An interconnection portion 30 is formed on
the first electrode 10. A pattern of the interconnection portion 30
is formed using, for example, photolithography and etching. Film
deposition (vacuum evaporation etc.) patterned by use of masks may
be used.
[0165] As shown in FIG. 18B, an organic light emitting layer 40 is
formed on the first electrode 10 and the interconnection portion
30. On the organic light emitting layer 40, a second electrode 20
is formed. In such a manner, a workpiece 110w is formed. The second
electrode 20 pattern is formed using, for example, photolithography
and etching. Film formation (evaporation etc.) by use of masks may
be used.
[0166] As shown in FIG. 18C, a light scattering film 50f forming
the light scattering layer 51 is formed on the back surface (a
processing surface 110ws) of the substrate 80 (which is a lower
surface and the opposite side surface of the substrate 80 with
respect to the first electrode 10). The light scattering film 50f
is, for example, photosensitive. The light scattering film 50f is a
photosensitive resin film 59. In this example, the light scattering
film 50f is taken to be positive in type.
[0167] As shown in FIG. 18D, the upper surface of the workpiece is
irradiated with an exposure light 75. The exposure light 75 is
blocked by the second electrode 20 (conductive portion 21) and the
interconnection portion 30 (interconnection layer 31). The light
scattering film 50f is irradiated with a portion of the exposure
light 75 that passes through a conductive portion non-formation
region 22 and an interconnection layer non-formation region 32.
[0168] Then, as shown in FIG. 18E, the portion of the light
scattering film 50f that is irradiated with the light can be
removed to form the light scattering layer 51.
[0169] In this example, the light scattering layer 51 is formed in
self-alignment with the second electrode 20 (conductive portion 21)
and the interconnection portion 30 (interconnection layer 31). The
shape of the light scattering layer 51 substantially overlays the
shapes of the second electrode 20 (conductive portion 21) and the
interconnection portion 30 (interconnection layer 31) and thus has
high processing accuracy. This method enables the light scattering
layer 51 to be easily manufactured.
[0170] FIG. 19A to FIG. 19D are schematic cross-sectional views
illustrating another method for manufacturing the organic
electroluminescent device according to the third embodiment in
order of processes.
[0171] As shown in FIG. 19A, for example, after forming the
workpiece 110w including the first electrode 10, the
interconnection portion 30, the organic light emitting layer 40,
and the second electrode 20 on the substrate 80, a photosensitive
resist film 58 is formed on the back surface of the substrate 80
(which is a lower surface and the opposite side surface of the
substrate 80 with respect to the first electrode 10). The resist
film 58 is the photosensitive resin film 59 and a negative-type
resist. Then, the upper surface of the workpiece is irradiated with
the exposure light 75. The exposure light 75 is blocked by the
second electrode 20 (conductive portion 21) and the interconnection
portion 30 (interconnection layer 31), so that the resist film 58
is irradiated with a portion of this exposure light 75 that passes
through the conductive portion non-formation region 22 and the
interconnection layer non-formation region 32.
[0172] As shown in FIG. 19B, for example, a portion of the resist
film 58 that is not irradiated with the light is removed.
[0173] As shown in FIG. 19C, the light scattering film 50f is
formed so as to cover the resist film 58 on the back surface (lower
surface) of the substrate 80.
[0174] As shown in FIG. 19D, the light scattering film 50f on the
resist film 58 is removed by removing the resist film 58. By this
method, the light scattering layer 51 is formed by processing the
light scattering film 50f by using the liftoff method.
[0175] In this example, the light scattering layer 51 is formed in
self-alignment with the second electrode 20 (conductive portion 21)
and the interconnection portion 30 (interconnection layer 31). The
shape of the light scattering layer 51 substantially overlays the
shapes of the second electrode 20 (conductive portion 21) and the
interconnection portion 30 (interconnection layer 31) and has
processing accuracy. This method enables the light scattering layer
51 to be easily manufactured.
[0176] FIG. 20 is a flowchart illustrating the method of
manufacturing the organic electroluminescent device according to
the third embodiment.
[0177] As shown in FIG. 20, in the manufacturing method, the
workpiece 110w is prepared (step S110). The workpiece 110w includes
the first electrode 10, the interconnection portion 30, the second
electrode 20, and the organic light emitting layer 40. The first
electrode 10 has a first major surface 10a and is light
transmissive. The interconnection portion 30 extends in a plane
parallel to the first major surface 10a and is electrically
connected to the first electrode 10. The interconnection portion 30
is more conductive than the first electrode 10 and is light
reflective. The first electrode 10 has a portion that does not
overlay the interconnection layer 31 when projected to the X-Y
plane. The second electrode 20 faces the first major surface 10a.
The second electrode 20 has a conductive portion 21. The conductive
portion 21 is light reflective. The conductive portion 21 is
provided on a portion of the region that does not overlay the
interconnection layer 31 when projected to the X-Y plane. The
conductive portion 21 is provided except in the conductive portion
non-formation region 22. The conductive portion non-formation
region 22 is provided on at least a portion of the region that does
not overlay the interconnection layer 31 when projected to the X-Y
plane. The organic light emitting layer 40 is provided between the
first major surface 10a and the second electrode 20.
[0178] For example, the first electrode 10 and the interconnection
portion 30 are formed on the light transmissive substrate 80, the
organic light emitting layer 40 is formed on the first electrode
10, and the second electrode 20 is formed on the organic light
emitting layer 40. For example, the processing described with
reference to FIG. 18A and FIG. 18B is performed.
[0179] Then, as shown in FIG. 20, the light scattering portion 50
is formed on the surface (the processing surface) of the workpiece
110w that is parallel to the X-Y plane by performing exposure
processing using the interconnection portion 30 and the second
electrode 20 as masks (step S120). The light scattering portion 50
is formed at a position where the first electrode 10 is disposed
between the light scattering portion 50 and the second electrode
20. In this step, the light scattering layer 51 is formed in a
region that overlays the interconnection layer 31 and the
conductive portion 21 when projected to the X-Y plane except at
least a portion that overlays none of the interconnection layer 31
and the conductive portion 21 when projected to the X-Y plane
(region on the surface of the workpiece 110w that is parallel to
the X-Y plane).
[0180] In the formation of the light scattering portion 50, for
example, the photosensitive resin film 59 is formed on the surface
of the workpiece 110w that is parallel to the X-Y plane. The resin
film 59 is formed at a position where the first electrode 10 is
disposed between the resin film 59 and the second electrode 20. The
resin film 59 is, for example, the light scattering film 50f. Then,
a process is included to irradiate the resin film 59 with the light
(exposure light 75) developing photosensitivity by using the
interconnection portion 30 and the second electrode 20 as masks to
shape the resin film 59 into a pattern on which the pattern shapes
of the interconnection portion 30 and the second electrode 20 are
reflected.
[0181] For example, the light scattering portion 50 is formed on
the lower surface of the substrate 80. In the formation of the
light scattering portion 50, the photo-reactive resin film 59
(light scattering film 50f) is formed on the lower surface of the
substrate 80. Then, the resin film 59 (light scattering film 50f)
is irradiated with the light (exposure light 75) coming from the
side of the upper surface of the substrate 80, by using the
interconnection portion 30 and the second electrode 20 as masks. In
such a manner, the resin film 59 (light scattering film 50f) is
processed into a pattern on which the pattern shapes of the
interconnection portion 30 and the second electrode 20 are
reflected. For example, the processing described with reference to
FIG. 18C and FIG. 18D is performed.
[0182] For example, the resin film 59 may be the resist film 58.
The resist film 58 is irradiated with the exposure light 75 by
using the interconnection portion 30 and the second electrode 20 as
masks so that the resist film 58 may be processed into a pattern on
which the pattern shapes of the interconnection portion 30 and the
second electrode 20 are reflected. Then, the light scattering film
50f is processed using the resist film 58 processed into the
predetermined pattern, thereby obtaining the light scattering layer
51. For example, the processing described with reference to FIG.
19A to FIG. 19D is performed.
[0183] In the first through third embodiments, by thinning the
conductive portion 21 and the interconnection layer 31 having
reflectivity, a region is provided which overlays neither of the
conductive portion 21 or the interconnection layer 31 when
projected to the X-Y plane. In such a manner, transparency is added
to the organic electroluminescent device. Then, by providing the
light scattering layer 51 in the region that overlays both of the
conductive portion 21 and the interconnection layer 31, the
formation of glare is suppressed. The light-extraction efficiency
of the emitted light 45 is improved. It is thus possible to improve
the luminous efficiency without decreasing the transmittance.
[0184] By reducing a line width of the conductive portion 21 and
the interconnection layer 31 or shaping them like a grid and
forming the line width so that it cannot be visually recognized,
the second electrode 20 and the interconnection portion 30 become
inconspicuous (cannot be visually recognized). As viewed from a
position distant by 1 m, the visually unrecognizable line width is,
for example, about not more than 100 .mu.m (for example, not more
than 120 .mu.m). For example, by setting the line width of the
conductive portion 21 and the interconnection layer 31 not more
than 120 .mu.m, the second electrode 20 and the interconnection
portion 30 cannot be visually recognized as a line.
[0185] In the organic electroluminescent device and the lighting
apparatus according to the embodiment, they can be realized to give
transparency so that a background image can be visually recognized,
well match an atmosphere, and have a luminous efficiency.
[0186] The embodiment provides optically transparent organic
electroluminescent device and lighting apparatus as well as a
method of manufacturing them.
[0187] Hereinabove, the embodiments of the invention have been
described with reference to the specific examples. However, the
embodiments of the invention are not limited to those specific
examples. For example, the specific configurations of the
components of the first electrode, the second electrode, the
interconnection layer, the organic light emitting layer, the light
scattering layer and the substrate included in the organic
electroluminescent device as well as the components such as the
power supply unit included in the lighting apparatus are covered by
the invention as long as those skilled in the art can obtain the
same effects by similarly carrying out the invention by
appropriately selecting them from the publicly known scope.
[0188] Further, any two or more components of the specific examples
may be combined within the extent of technical feasibility and are
included in the scope of the invention to the extent that the
purport of the invention is included.
[0189] Moreover, all organic electroluminescent devices practicable
by an appropriate design modification by one skilled in the art
based on the organic electroluminescent devices, the lighting
apparatus and the method for manufacturing the electroluminescent
device described above as embodiments of the invention also are
within the scope of the invention to the extent that the spirit of
the invention is included.
[0190] Various other variations and modifications can be conceived
by those skilled in the art within the spirit of the invention, and
it is understood that such variations and modifications are also
encompassed within the scope of the invention.
[0191] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
invention.
* * * * *